The present invention generally relates to a method and apparatus for taking samples of an analog television signal that is particularly suited for use in a magnetic recording and reproducing apparatus.
As is comprehensively set forth in our copending patent application Ser. No. 117,428, a digital recording and reproducing apparatus is disclosed which has many significant advantages compared to most commercial quality television broadcasting recording and reproducing apparatus which record and reproduce FM signals. In our aforementioned application, pluse code modulated digital video signals are recorded and reproduced. The digital recording and reproducing apparatus has, when compared to FM recording and reproducing, the desirable attributes of virtually eliminating banding and Moire of any nature from any cause, reducing chroma and luminance noise to a value better than -54 db, relaxing mechanical tolerances for quadrature adjustments in a quadruplex format recording apparatus by a factor of about 100 and providing an inherent time base error that is no greater than about 1/2 nanosecond.
The present invention also enables the aforementioned recording and reproducing apparatus to eliminate the problem of cycle hops which is present in conventional video tape recorders, for the reason that the decision for making the zero crossing selection for sampling the television signal is precisely determined with respect to the location of a horizontal synchronization pulse which is generated and which is precisely defined with respect to color burst phase and therefore the phase of the unmodulated color subcarrier and this is done before recording so that consistent reliable reproducing can be achieved.
The present invention is also broadly applicable to information signals other than a composite color television signal provided that the information signal is of the type which has a time-base synchronizing component. Such signals are used in wideband telemetry systems wherein the wideband telemetry signal has a pilot signal that represents the time-base synchronizing component.